Liquid crystal display arrangements

Abstract

A liquid crystal display arrangement is provided with two liquid crystal cells containing twisted-nematic material, and positoned one cell behind the other. Both cells are between a pair of crossed polarizers, and the arrangement can be used to selectively reverse the contrast of a display or it can be used as a matrix display in which cross-talk between adjacent elements is minimized.

We claim: 
     
       1. A liquid crystal display arrangement including two planar liquid crystal cells placed one behind the other, both cells containing twisted-nematic liquid crystal material and being positioned between a pair of crossed polarizers, and matrix means associated with each cell for addressing selected areas of the display arrangement, each said matrix means comprising discrete conductive stripes defining a row-column matrix, one matrix being adapted to have applied thereto row and column address voltages which are of relatively opposite polarities and the other matrix being adapted to have applied thereto row and column address voltages which are of the same polarities so that the optical rotations effected by the address voltages of the two cells at the cross talk areas thereof have a combined effect which is subsantially removed by the last polarizer. 
     
     
       2. A liquid crystal display arrangement as defined in claim 1 wherein said polarizers are crossed at 90°. 
     
     
       3. A liquid crystal display arrangement as defined in claim 1 wherein said polarizers are crossed at 45°. 
     
     
       4. A liquid crystal display arrangement as defined in claim 1 wherein said address voltages are much greater than the threshold voltage of said twisted nematic liquid crystal material. 
     
     
       5. A liquid crystal display arrangement as defined in claim 4 wherein said polarizers are crossed at 90°. 
     
     
       6. A liquid crystal display arrangement as defined in claim 4 wherein said polarizers are crossed at 45°. 
     
     
       7. The method of displaying a discrete area of a liquid crystal arrangement, which comprises the steps of: (a) providing a pair of planar liquid crystal cells one behind the other between a pair of crossed polarizers, each cell containing twisted nematic liquid crystal material and each cell having a row-column matrix of conductive stripes for address purposes;   (b) addressing the matrix of one cell with row and column voltages having the same relative polarities; and   (c) addressing the matrix of the other cell with row and column voltages having opposite relative polarities.   
     
     
       8. The method of claim 7 wherein said row and column voltages are of values much greater than the threshold voltage of said liquid crystal material. 
     
     
       9. The method of claim 8 wherein said polarizers are crossed at 90°. 
     
     
       10. The method of claim 8 wherein said polarizers are crossed at 45°.